Aromatic compounds Aziridine

In some cases, oxidations have been placed in another chapter. The oxidation of an alkene to a diol (15-48), and aromatic compound to a diol (15-49), or oxidation to an epoxide (15-50) are placed in Chapter 15, for consistency with the concept of addition to a 7i-bond. Diamination of an alkene (15-53) and formation of aziridines (15-54) are in Chapter 15 for the same reason. Most other oxidations have been placed here. The reactions in this section are classihed into groups depending on... 

Treatment of aryl azides with AICI3 has been reported to give polycyclic aromatic compounds (eq 7), or aziridines when the reactions are run in the presence of aUcenes (eq 8). ... 

The latter reacts with a second DMAD molecule to give cycloadduct (726). The reaction proceeds via opening of the aziridine ring to give compound (725). The cyclo-adduct (726) undergoes a 1,3-sigmatropic shift and aromatization to give compound (723) (Scheme 2.302) (816). 

In contrast to the epoxides, preparative routes to the aziridines are fairly evenly split between the [C=N + C] and the [C=C + N] routes. Among contributions in the former category, aziridine carboxylate derivatives 110 can be prepared through the lanthanide-catalyzed reaction of imines with diazo compounds, such as ethyl diazoacetate (EDA). In this protocol, iV-benzyl aryl aldimines and imines derived from aromatic amines and hindered aliphatic aldehydes are appropriate substrates <99T12929>. An intramolecular variant of this reaction (e.g.. Ill —> 112) has also been reported <990L667>. 

Synthesis of annelated diazepines based on unsaturated aromatic diazepines may involve the preliminary transformation of ketones into the corresponding l,3-diaryl-2,3-dibromopropane-3-ones (chalcone dibromides). The interaction between o-PDA or some of its substituted analogues with chalcone dibromides leads to the formation of aziridine derivatives [64] (see Chap. 1). However, in the case of 4-nitro-o-PDA, either azirenoquinoxalynes 53 or benzodiazepine derivatives 54 may be obtained depending on the reaction conditions [65] (Scheme 4.15). Diazepine derivatives 56 are obtained by the condensation of chalcone dibromides 51 with 5,6-diamino-1,3-dimethyluracil 55 [66], but aziridine derivatives are not isolated in this reaction. It should be noted that compounds 54 and 56 are formed owing to cyclization of the intermediate (3-enaminoketones [65, 66, 67] and are easily isolated from the reaction mixture. 

On this ground, DCA was found a suitable sensitizer to induce the photooxygenation of a great variety of organic compounds such as alkenes [84,94-98], alkynes [99,100], sulfides [84,98,101], dienes [84], sulfoxides [102], cycloalkanes [103,104], cycloalkenes [105,106], epoxides [107,108], aziridines [109], allenes [110], dioxenes [111], p-dioxins [111,112], aromatic substrates [113], tertiary amines [114], and of great interest from the mechanistic point of view, sterically hindered olefines [97,115-117]. 

Ethyleneimine (aziridine) and carbon-substituted alkyleneimines are relatively weakly basic compounds [43, 44], This is ascribed to 71-electron delocalization in the ring [44]. By protonation of the imine cycle this aromaticity disappears, and iminium rings are much more readily broken than imines [45], Also the N-alkylethyleneimines are only weakly basic, and they are also more resistant to ring-opening nucleophilic reactions [46]. 

Reaction of aziridino alcohols with Lewis acids provides /3-amino carbonyl compounds in excellent yields <20020L363, 20030L2319>. Treatment of aziridine 181 with ZnBt2 at room temperature initiates a migration of the aromatic ring to provide aldehyde 182 as a single diastereomer in 96% yield (Equation 51). 

Oxygen reacts readily with aromatic sulfides [341], AT-methionyl peptides [342], 1,3-dithianes [343], aziridines [344], and phosphorus [345] compounds after oxidation. On the other hand, aryl radicals are involved in the ET reaction of trivalent phosphorus compounds with aromatic diazonium salts [346]. 

Other examples have been provided by the anodically initiated isomerization of several decarbene metal carbonyl couples [197]. Electrochemical induction of chemical reactions can also be successfully used for conversion of alcoolates into ketones with simultaneous reduction of aromatic halides [198], the tetramerization of aziridines [199], or ligand substitution [200] in organometallic compounds. A useful review on this subject was published [201]. 

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